Electronic interfaces are commonly used in a wide range of applications from consumer products including computer systems, game consoles, electrical appliances, in-vehicle systems including automotive consoles or central stacks and wheel mounted controls, portable devices including audio devices, multimedia players, cellular phones or the like, to industrial control consoles, switches, or the like. While mechanical buttons, switches, contacts and the like have typically been used in connection with conventional electronic input devices, there has been a shift away from the use of mechanical buttons, switches and the like toward low activation pressure technologies such as touch sensitive switches. Integrating touch sensor technologies into input devices in connection with products such as touch panels, touch screens, and capacitive keypads and the like has increased due to the development in capacitive sensing technologies. Such technologies generally locate the area of touch sensitivity within the bounds of a flat region on a panel of a device such as a display or the like, which can be glass, plastic, film or the like, and is often located over a display.
It will be appreciated however that, while advantages can be gained by the use of touch sensitive controls on computer screens and flat panel input areas, certain limitations exist for integrating touch sensitive technology into moulded articles. Currently, regardless of the desired shape of the device, the design is predominated by the need for a flat area into which or onto which a touch sensitive input device can be mounted. The electronics and plastic parts are generally then assembled to form a product requiring multiple steps of subassembly integration, test, final assembly, final test and the like. Touch sensitive areas are required to be flat because there are generally no known touch sensor switches and or other film based technology that can be readily integrated into a shaped structure having contours within the touch sensitive areas.
In recent years, due to the development of better printing methodologies and inks with special functions such as conductive inks, and the like, film insert moulding (FIM) processes have been used to manufacture touch sensor devices and lighting devices, e.g. using electroluminescent (EL) technologies in connection with film articles. Further, FIM process has been used to incorporate elements such as a switches and the like into film articles. After the printing and forming process is completed and a film article is produced, the printed film articles can be further subjected to moulding processes including: injection moulding or thermoforming processes.
For example, resistive and shielded elements are disclosed in International Application Publication Number WO 2009/128856, and a capacitive switch is disclosed in International Application Publication Number WO 2008/131305 to Haag, et al. While Haag describes various configurations in which films using conductive inks can be formed, the problem of cracking during formation is acknowledged. Haag fails to describe how to select variables associated with the ink avoid cracking. Haag avoids spanning the inks within the sensing zones and does not propose to substantially solve problems associated with cracking and the like in those zones.
Still further, while capacitive switches and lighting materials have been used in electronic devices, integrating known touch sensitive elements and lighting into film structures has posed challenges, although conventional FIM capacitive touch panels are available in 2-dimensional form. FIG. 1 shows an assembly of parts that make up a prior art touch panel 100. In particular, touch panel 100 can include a formable film 105, a graphic layer 104, and a plurality of layers 101, 102, 103. The plurality of layers 101, 102, 103 may consist of conductive ink printed on the graphic layer 104 to form a touch sensor zone. However, layers formed from such conductive inks are generally brittle and are susceptible to cracking during forming processes as is acknowledged in the art.